Transmission over a serial link using clock forwarding is used in multimedia streaming applications such as HDMI™ (High Definition Multimedia Interface, including High Definition Multimedia Interface 1.4 Specification, issued May 28, 2009) and MHL™ (Mobile High-Definition Link) for the overall system simplicity and improved noise performance of such transmission. MHL is an interface protocol that provides for connection of a mobile device to an HDMI display device. Such protocols allow for the transfer of high definition multimedia data between certain devices.
One of the drawbacks of a clock forwarding scheme is the use of a clock channel. In terms of bandwidth utilization, a dedicated clock channel requires additional overhead compared to a CDR (Clock and Data Recovery) based serial link because the clock channel doesn't convey any data. In addition, in some cases, there are physical limitations on number of connector pins or cable wires in an apparatus, which complicates or prevents the use of a dedicated clock channel.
U.S. Pat. No. 6,463,092 of Kim, et al., regards sending and receiving data signals over a clock signal line, including a transmitter that sends both clock and data signals over the same transmission line and a receiver that uses the same transmission line to transmit data signals back to the transmitter.
United States Patent Application Publication No. 2010/0104029 of Lee, et al., regards independent links over differential pairs using common-mode signaling, including pairs of differential pairs being utilized to create a virtual differential pair for data transfer.